A phase 1 study of an injectable lidocaine paste for spermatic cord block in men with chronic scrotal content pain

INTRODUCTION: Patients with chronic scrotal content pain (CSCP) lack effective, non- invasive treatment options. We aimed to determine the local and systemic safety, tolerability, pharmacokinetics (PK), and efficacy of a long-lasting local anesthetic in patients with CSCP. METHODS: This was a prospective, single-center, open-label, single-arm, phase 1, dose- escalating trial completed between October 2019 and March 2021. Twelve patients >= 19 years old with unilateral scrotal pain lasting >= 3 months reporting an average maximum pain score over seven days of >= 4 on a 0-10 numerical rating scale (NRS) were included. Patients underwent a test spermatic cord block and those reporting a decrease of >= 2 points were included. The investigational drug, ST-01 (sustained-release lidocaine polymer solution), is a long-acting injection of lidocaine around the spermatic cord. Subjects were provided a NRS dairy and recorded their NRS score until day 28. The Chronic Epididymitis Symptom Index (CESI) was completed on days 0, 7, 14, and 28. All patients underwent an examination and assessment for adverse events (AE) on days 0, 1, 7, 14, and 28. Exploratory statistical hypothesis testing was planned for this study due to its investigative nature. RESULTS: There were no serious adverse events (SAEs) reported. All subjects reported at least one treatment-emergent adverse event (TEAE); 83% of related AEs were injection-site reactions consisting of swelling and bruising. NRS was reduced across all cohorts between baseline and end of study. CONCLUSIONS: This study provides evidence that the novel ST-01 treatment is safe and well-tolerated.